Refractory pouring tube for degassing vessels



Nov. 21, 1967 R. SNELLMAN RERACTORY POURING TUBE FOR DEGASSING VESSELS Filed NOV. 2. 1965 l N VEN TOR.

/PE/P SNEL L M4N United States Patent O 3,353,809 REFRACTORY POURING TUBE FOR DEGASSING VESSELS Roger Snellman, 5746 Raven Road, Birmingham, Mich. 48010 Filed Nov. 2,- 1965, Ser. No. 506,096 3 Claims. (Cl. 2156-34) This invention relates to vacuum degassingrdevices and more particularly to conduit for joining degassing charnbers with ladles.

As the requirement for metals with improved properties has continued to increase, the metals industry has had to turn. to more contemporary techniques to improve product. -One such technique is to remove entrapped gases that are acquired by the metal during the refining processes. Generally speaking, these gases can cause brittleness in the metal. Techniques and equipment for removing these gases while the metal is still molten are several. One apparatus, for example, is known as the Dortmund-Horder degasser. In this apparatus, an enclosed vacuum chamber with a conduit attached in open communication with its base is positioned over a ladle of molten-steel. The conduit is immersed in the molten steel, a vacuum drawn upon the chamber, and molten metal rushes up through the conduit into the'chamber releasing entrapped gases. After the chamber is nearly lled, the vacuum is released and the molten metal returns to the ladle. This process is often repeated many times before the desired low gas level is obtained.

In another type of degassing apparatus, two conduits are attached in open communication with the base of the degassing chamber. The metal is drawn up through one conduit and returns to the ladle through another.

Conduits joining degassing chambers and ladles have been constructed of a combination of refractory brick and monolith, mortar and metal. A metal pipe or conduit forms the skeleton or support against which the refractories are placed. Conduits of this type have not been altogether successful. One disadvantage results primarily from difference in coefllcient of thermal expansion between the metal and refractories; that is, the metal pipe expands on heat-up more than the refractory coating which leads to loosening of the refractories and ultimately to failure.

It has also been suggested to provide ceramic conduits of different diameters so that they can be arranged concentrically with a metal conduit placed therebetween. The metal tube is necessary because ceramic conduit of the prior art has been considered too permeable to permit a vacuum to be drawn on the degassing chamber. This construction has been stated to obviate the problems of the previously discussed type of conduit construction. But, this also has not been altogether satisfactory. For example, the metal tube is not protected by an insulating layer of refractory and, therefore, may become Warped and even melt. Furthermore, gaps between the concentric ceramic conduit and the metal tube must be lled. Some requirements of this till material are that it be compressibleto accommodate the different thermal expansion of the metal tube and the ceramic; and, at the same time, it must be resistant to attack by hot metal. This is one of the same problems faced with the brick and metal conduit construction.

In addition to the requirements outlined above, degassing chambers with ladles should be resistant to corrosion and abrasion by the washing action of hot metal and possibly slag. The conduit should be well bonded so that particles of refractory do not crumble away and contaminate the metal being treated. Furthermore, the conduit should not be susceptible to spalling due to rapid temperature change.

3,353,809 Patented Nov. 21, 1967 rice It is therefore an object of this invention to provide a device for degassing molten metal having a conduit for drawing molten metal into the degassing chamber, which conduit is not easily eroded by the washing action of molten metal and slags, which is not susceptible to spalling caused by rapid change in temperatures, which does not react with metal, which is nearly impermeable, and which has a tight structure, i.e., one which does not develop free play between parts easily.

Briefly, according to one aspect, the objects and advantages of this invention are achieved in a device for degassing molten metal comprised of a ladle for containing the molten metal, a chamber for removing the gases from the metal that is positioned above the ladle and has a conduit attached in open communication with the degassing chamber so that when the vacuum is applied to the chamber molten metal can be drawn through the conduit from the ladle. The conduit is comprised of a plurality of cooperative interlocking cylinders. There is an inner cylinder of high purity dead burned magnesite shapes. A cylinder of insulating refractories shapes contiguously surrounds' the major extent of the inner cylinder. A metal supporting cylinder contiguously surrounds the major extent of the insulating refractory cylinder. There are metal flanges extending from the inner surface of the metal cylinder to support the magnesite and insulating refractory cylinders. A cylinder of asbestos board is adjacent both inner and outer surfaces of the metal supporting cylinder. An additional cylinder of high alumina monolithic refractory material held in place by metal anchors extending from the outer surface of the metal cylinder substantially entirely covers the asbestos cylinder. There is a rim attached to the lower end of said conduit comprised of dense high alumina refractory shapes.

This invention is more clearly understood by reference to the attached diagram. It is exemplary of only one mode of practicing this invention and, therefore, is offered by way of explanation and not by way of limitation.

The diagram is a sectional view through a vacuum degasser andthe attached conduit.

The body of the vacuum degasser 10 has an opening 11 in its oor 12. Connected in open communication with the degassing chamber is a conduit 14. The conduit is comprised of a plurality of concentric cylinders. There is an inner cylinder 15 fabricated of high purity dead burned magnesite shapes. Contiguously surrounding the inner cylinder of magnesite shapes is a cylinder 16 of insulating brick shapes. A metal supporting cylinder 17 surrounds the major extent of the insulating refractory cylinder. It has metal flanges 18 which support the magnesite and insulating refractory cylinders. It also has anchors 19 substantially entirely covering its outer surface. Adjacent the metal cylinders inner and outer surface are cylinders of a compressible refractory material 20 and 21, for example, asbestos. An additional cylinder 22 of high alumina monolithic refractory covers substantially entirely the asbestos cylinder 21. There is a rim 23 comprised of dense high alumina refractory shapes at the lower end of the conduit. The conduit is attached to the vacuum chamber by fastener means 24.

The advantages ofthe construction outlined above over the prior art are several. There is provided a tight structure with no open spaces which structure remains tight upon heating and cooling. The inner lining is comprised of high purity magnesite brick which has almost no tendency to react with molten metal and is very refractory, thereby having little tendency to be eroded by the molten metal. The portion of the conduit receiving the most extreme abrasion is the lower rim. This rim has been constructed of a very dense, high alumina refractory known for its resistance to abrasion. The insulating refractory layer provides two functions. First, it keeps a shallow thermal gradient through the magnesite cylinder thereby reducing its tendency to thermal spalling. Second, the insulating layer maintains the metal cylinder at a temperature sufciently low that it does not lose its structural strength required to support and contain the Whole conduit. The compressible layers allow for the different expansion between the metal cylinder and the surrounding ceramic refractory cylinders and at the same time maintain a tight structure. The outer cylinder of high alumina monolithic refractory protects the outer surface of the metal shell. It is not necessary nor advantageous to use burned shapes in the outer cylinder as there is little abrasive wear on this area. It is easily chipped away and rebuilt. The anchors provide strong support for the monolithic layer. This construction having many elements -overcomes the problems of the prior art by uniquely combining several very dissimilar materials.

While the conduit described above has been discussed in relationship to a degassing vessel, it is obvious that it is of use in transferring molten metal from one vessel to another by any process whereby the metal is transferred by a differential pressure.

Having thus described the invention in detail and with sufficient particularity as to enable those skilled in the art to practice it, what is desired to have protected by Letters Patent is set forth in the following claims.

What is claimed is:

1. A device for degassing molten metal comprised of ladle means for cortaining molten metal, chamber means for removing gases from said metal, said chamber means positioned above said ladle means, and conduit means, said conduit means having an upper and a lower end, said conduit means being xed in open communication at its upper end to said chamber means and positioned for immersion of its lower end into said ladle means; said conduit means being comprised of a plurality of concentric, cooperatively interlocking cylinders, said cylinders being comprised of:

an inner cylinder of high purity dead burned magnesite shapes,

a cylinder of insulating refractory shape contiguously surrounding the major extent of said inner cylinder,

a metal supporting cylinder contiguously surrounding the major extent of said insulating refractory cylinder, said cylinder having inner and outer surfaces, there being metal flanges extending from the inner surface to support said magnesite and insulating refractory cylinders, there being metal anchors extending from said outer surface,

a cylinder of asbestos board adjacent both inner and outer surfaces of the metal supporting cylinder,

an additional cylinder of high alumina monolithic refractory held in place by said anchors substantially entirely covering the asbestos covering said outer surface of said metal cylinder and,

there being a rim attached at said lower end of said conduit comprised of dense high alumina refractory shapes.

2. A conduit means for transferring molten metal from one vessel to another by providing a differential pressure, said conduit means being comprised of a plurality of concentric, cooperatively interlocking cylinders, said cylinders being comprised of:

an inner cylinder of high purity dead burned magnesite shapes,

a cylinder of insulating refractory shapes contiguously surrounding the major extent of said inner cylinder,

a metal supporting cylinder contiguously surrounding the major extent of said insulating refractory cylinder, said cylinder having inner and outer surfaces, there being metal flanges extending from the inner surface to support said magnesite and insulating refractory cylinders, there being metal anchors extending from said outer surface,

a cylinder of asbestos board adjacent both inner and outer surfaces of the metal supporting cylinder,

an additional cylinder of high alumina monolithic refractory held in place by said anchors substantially entirely covering the asbestos covering said outer surface of said metal cylinder and,

there being a rim attached at said lower end of said conduit comprised of dense high alumina refractory shapes.

3. A device for degassing molten metal comprised of ladle means for containing molten metal, chamber means for removing gases from said metal, said chamber means positioned above said ladle means, and conduit means, said conduit means having an upper and a lower end, said conduit means beging fixed in open communication at its upper end to said chamber means and positioned for immersion of its lower end into said ladle means', said conduit means being comprised of a plurality of concentric, cooperatively interlocking cylinders, said cylinders being comprised of:

an inner cylinder of high purity dead burned magnesite shapes,

a cylinder of insulating refractory shapes contiguously surrounding the major extent of said inne-r cylinder,

a metal supporting cylinder contiguously surrounding the major extent of said insulating refractory cylinder, said cylinder having inner and outer surfaces, there being metal flanges extending from the inner surface to support said magnesite and insulating refractory cylinders, there being metal anchors extending from said outer surface,

a cylinder of compressible refractory material adjacent both inner and outer surfaces of the metal supporting cylinder,

an additional cylinder of a material selected from the group consisting of reclay and high alumina monolithic refractories, held in place by said anchors substantially entirely covering said outer surface of said metal cylinder and, f

there being a rim attached at said lower end of said conduit comprised of dense abrasive resistant refractories.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 7/ 1961 Germany.

I. SPENCER OVERHOLSER, Primary Examiner,

E. MAR, Assistant Examiner, 

3. A DEVICE FOR DEGASSING MOLTEN COMPRISED OF LADLE MEANS FOR CONTAINING MOLTEN METAL, CHAMBER MEANS FOR REMOVING GASES FROM SAID METAL, SAID CHAMBER MEANS POSITIONED ABOVE SAID LADLE MEANS, AND CONDUIT MEANS, SAID CONDUIT MEANS HAVING AN UPPER AND A LOWER END, SAID CONDUIT MEANS BEGING FIXED IN OPEN COMMUNICATION AT ITS UPPER END TO SAID CHAMBER MEANS AND POSITIONED FOR IMMERSION OF ITS LOWER END INTO SAID LADLE MEANS; SAID CONDUIT MEANS BEING COMPRISED OF A PLURALITY OF CONCENTRIC, COOPERATIVELY INTERLOCKING CYLINDERS, SAID CYLINDERS BEING COMPRISED OF: AN INNER CYLINDER OF HIGH PURITY DEAD BURNED MAGNESITE SHAPES, A CYLINDER OF INSULATING REFRACTORY SHAPES CONTIGUOUSLY SURROUNDING THE MAJOR EXTEND OF SAID INNER CYLINDER, A METAL SUPPORTING CYLINDER CONTIGUOUSLY SURROUNDING THE MAJOR EXTENT OF SAID INSULATING REFRACTORY CYLINDER, SAID CYLINDER HAVING INNER AND OUTER SURFACES, THERE BEING METAL FLANGES EXTENDING FROM THE INNER SURFACE TO SUPPORT SAID MAGNESITE AND INSULATING REFRACTORY CYLINDERS, THERE BEING METAL ANCHORS EXTENDING FROM SAID OUTER SURFACE, A CYLINDER OF COMPRESSIBLE REFRACTORY MATERIAL ADJACENT BOTH INNER AND OUTER SURFACES OF THE METAL SUPPORTING CYLINDER, AN ADDITIONAL CYLINDER OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF A FIRECLAY AND HIGH ALUMINA MONOLITHIC REFRACTORIES, HELD IN PLACE BY SAID ANCHORS SUBSTANTIALLY ENTIRELY COVERING SAID OUTER SURFACE OF SAID METAL CYLINDER AND, THERE BEING A RIM ATTACHED AT SAID LOWER END OF SAID CONDUIT COMPRISED OF DENSE ABRASIVE RESISTANT REFRACTORIES. 